Is your attitude the decisive factor to your success?

Yes...
If you dont have a positive attitude your employer and manager will not want you around too long.
Ability is also important; but your attitude will determine how people in your workplace perceive you. 

Yes, your attitude is the most important factor influencing peple, but attitude does not mean arrogance there is a very thin line between attitude and arrogance, having positive attitude means doing things the right way being courtious and polite and helping others in their work and being resourceful this definatley leads to increase in your knowledge and helps you grow as a professional